feat: Add hybrid search support for Bedrock KB

[gingerknight]

Summary

Add hybrid search (vector + keyword) for Bedrock Knowledge Base repositories. When an admin enables hybrid search and a repository supports it, sessions default to hybrid mode. The feature includes automatic fallback to vector-only for unsupported knowledge bases.

Key behaviors:

• Admin toggle acts as a hard gate — disabling forces all sessions to vector regardless of user selection
• UI shows a search mode selector only when the repository supports hybrid
• Citations display which search mode was actually used (Hybrid vs Vector fallback)
• Chat Assistant stacks correctly activate hybrid when their configured repository supports it

Breaking change (SDK)

lisapy.RagMixin.similarity_search() now returns dict instead of list[dict]:

  # Before
  docs = client.similarity_search(query, repository_id, top_k=3)

  # After
  result = client.similarity_search(query, repository_id, top_k=3)
  docs = result["docs"]
  metadata = result["metadata"]  # search_mode, actual_mode_used, backend, hybrid_supported

Test plan

• Unit tests pass: npm run test:lambda, frontend npm test
• Deployed to dev account and verified hybrid badge displays correctly
• Session save/load preserves hybrid search mode selection
• Chat Assistant stack shows hybrid selection dropdown

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[Copilot]

Pull request overview

Adds hybrid (vector + keyword) retrieval for Bedrock Knowledge Base (KB) repositories and propagates a search_mode selection end-to-end (SDK → Lambda → repository service → UI), including UI affordances to show when hybrid was used vs vector fallback.

Changes:

• Backend: introduce supports_hybrid_search() / hybrid_retrieve() on RepositoryService, implement Bedrock KB hybrid retrieval with targeted fallback, and route requests via searchMode in the repository Lambda.
• SDK + API consumers: extend similarity_search() to accept search_mode and return a structured { docs, metadata } response.
• Frontend: capability-gated “RAG Search Mode” selector, request propagation, and citations header badge indicating Hybrid vs Vector(fallback), plus persistence + tests.

Reviewed changes

Copilot reviewed 31 out of 31 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
test/sdk/test_sdk_rag.py	Updates SDK RAG tests for new similarity_search() return shape; adds search_mode/metadata tests.
test/sdk/test_evaluation_runner.py	Adjusts evaluation runner tests to the new { docs: [...] } return format.
test/lambda/test_session_lambda.py	Adds round-trip persistence tests for supportsHybridSearch and ragSearchMode.
test/lambda/test_repository_lambda.py	Adds tests for repo listing capability flag and searchMode routing/metadata behavior.
test/lambda/repository/services/test_repository_service.py	Tests default hybrid-support behavior in the base repository service.
test/lambda/repository/services/test_bedrock_kb_repository_service.py	Adds Bedrock KB hybrid retrieve tests, including fallback + error propagation.
test/integration/rag/test_rag_collections_integration.py	Updates integration test to consume results["docs"].
lisa-sdk/lisapy/rag.py	SDK adds search_mode / include_score and returns structured response with optional metadata.
lisa-sdk/lisapy/evaluation/lisa_api.py	Updates evaluator to read from results["docs"].
lib/user-interface/react/src/shared/reducers/rag.reducer.ts	Adds searchMode param, changes relevant-docs response type, always requests scores.
lib/user-interface/react/src/shared/reducers/rag.reducer.test.ts	Tests query builder URL composition for searchMode and score=true.
lib/user-interface/react/src/shared/model/configuration.model.ts	Introduces enabledComponents.hybridSearch flag.
lib/user-interface/react/src/shared/model/configuration.model.test.ts	Tests defaulting/acceptance for hybridSearch.
lib/user-interface/react/src/shared/model/chat.configurations.model.ts	Adds ragSearchMode to session configuration defaults.
lib/user-interface/react/src/shared/model/chat.configurations.model.test.ts	Tests ragSearchMode default is vector.
lib/user-interface/react/src/components/types.tsx	Adds RagSearchMetadata and typed citation shape.
lib/user-interface/react/src/components/Topbar.test.tsx	Refactors menu interaction helper for JSDOM/Cloudscape rendering behavior.
lib/user-interface/react/src/components/configuration/ActivatedUserComponents.tsx	Adds “Hybrid search” as an activated component label.
lib/user-interface/react/src/components/chatbot/utils/messageBuilder.utils.tsx	Structures citations with similarity score; extracts ragSearchMetadata.
lib/user-interface/react/src/components/chatbot/utils/messageBuilder.utils.test.tsx	Tests citation structuring and metadata extraction behavior.
lib/user-interface/react/src/components/chatbot/components/SessionConfiguration.tsx	Adds capability-gated “RAG Search Mode” selector.
lib/user-interface/react/src/components/chatbot/components/SessionConfiguration.test.tsx	Tests showing/hiding the selector based on flags and repo capability.
lib/user-interface/react/src/components/chatbot/components/RagOptions.tsx	Plumbs supportsHybridSearch from repo list into ragConfig.
lib/user-interface/react/src/components/chatbot/components/Message.tsx	Adds Hybrid / Vector(fallback) badge in citations header.
lib/user-interface/react/src/components/chatbot/Chat.tsx	Sends searchMode in relevant-docs request; warns when hybrid falls back.
lib/chat/api/configuration.ts	Enables hybridSearch component flag when RAG is deployed.
lambda/shared/python/lisa/session/models.py	Adds ragSearchMode and supportsHybridSearch to session models.
lambda/shared/python/lisa/rag/services/repository_service.py	Adds base supports_hybrid_search() and hybrid_retrieve() API.
lambda/shared/python/lisa/rag/services/bedrock_kb_repository_service.py	Implements Bedrock KB hybrid retrieve with narrowed ValidationException fallback.
lambda/handlers/repository/lambda_functions.py	Adds supportsHybridSearch to repo listing; routes similarity search by searchMode and returns search metadata.
.pre-commit-config.yaml	Extends detect-secrets exclude patterns to include .test.ts.

Comments suppressed due to low confidence (1)

lisa-sdk/lisapy/rag.py:214

• params sets repositoryType to repo_id, but this query param is not used by the backend similaritySearch handler and the value is not actually a repository type. Sending an incorrect/unused parameter is confusing and could break if server-side validation is added later; consider removing it (or renaming/setting it correctly if needed).

        url = f"{self.url}/repository/{repo_id}/similaritySearch"
        params: dict[str, str | int] = {"query": query, "repositoryType": repo_id, "topK": k}

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